Emma McKeon says her coveted individual gold is the sweetest of all as she swims to the edge of Australian Olympic history.

McKeon won gold and compatriot Cate Campbell bronze in Friday's 100-metres freestyle at the Tokyo Olympics.

It was McKeon's eighth Olympic career medal, but first individual gold.

"I've never won an Olympics or worlds (world championships) individual title," said McKeon, who clocked a winning time of 51.96 seconds - a new Olympic record.

"That's what the Olympics is all about. To be able to stand on top of that podium.

"I never started to wonder or lose belief of anything like that. I definitely had belief in myself and that built over the last two years.

"But to actually pull it off is a totally different thing ... I am over the moon."

McKeon joins Ariarne Titmus as dual gold medallists in Tokyo.

McKeon - who also has two bronze - is one shy of equalling the Australian record for most medals at a single Olympics.

Swim legends Ian Thorpe and Shane Gould are the only Australians with five medals at one Games.

And McKeon could still add two more golds, in the 50m freestyle and 4x100m mixed medley relay.

Should McKeon collect six medals in Tokyo, not only would it be a new Australian benchmark at a single Games.

She would also be the first Australian with a double-figure medal collection, surpassing Thorpe's nine - five gold, three silver and a bronze - in his fabled career.

The 100m podium was completed by Hong Kong's Siobhan Haughey (52.27 seconds) and Campbell (52.52).

Four-time Olympian Campbell now has three gold and three bronze career medals and is also a shot at the 50m freestyle.

Campbell's 100m bronze also goes some way to banishing the disappointment of her sixth in Rio when she entered as world record holder.

"There were understandably quite a few demons knocking at the door when I woke up this morning," Campbell said.

"But I held them all at bay and performed when it counted to get another Olympic medal."

Campbell hailed McKeon as "one of the toughest competitors and trainers that I've ever encountered".

"She deserves everything that has come her way," she said.

In the women's 200m backstroke semi-finals, Australia's Kaylee McKeown and Emily Seebohm both advanced to the medal race.

Veteran Seebohm, at her fourth Olympics, was fastest into the final in two minutes 07.09 seconds.

McKeown, the 100m backstroke gold medallist, was second in her semi and fifth-quickest overall in 2:07.93.

And Australia's Matt Temple advanced to the final of the 100m butterfly, sixth-fastest through the semis in 51.12, with 100m freestyle champ Caeleb Dressel (49.71) of the United States an unbackable favourite to win gold.